Process for the treatment of plant flesh and the recovery of pectic products therefrom



Patented Feb. 18,1947 2 ,4l6,l76 I 1 UNITED STATES PATENT "@OFFICEji v.2,416,1l'6' 1 PROCESS [FOR THE TREATMENT OF PLANT-' FLESH ANDTHERECOVERY OF PECTIC raonncrs THEREFROM Thomas Percy Hoar, Cambridge,andElsie Lilian James, Bulstrode,. Gerrards Cross, England, assignors toAfrican Sisal & Produce Company Limited, Bulstrode, England, a companyof 'Great Britain No Drawing. Application June 3, 1944, Serial N0.538,689. In Great Britain February 14, 1944 V v 6 Claims.

cular reference to the utilisation of the fleshy material obtained fromthe vegetable matter phormium tenax.

In the commercial extraction of fibres from sisal and like plants,whether the extraction be by wet or dry decortication, or as a result ofsisal plant, and like including sansevieria and The invention consistsin an improved process for the treatment of plant flesh of the typeabove indicated, and in the recovery of pectic products therefrom, bythe removal of said inhibitory factors, colouring matters anddegenerated products while substantially avoiding extraction of pecticsubstances from the flesh, by preparation processes which embracesubjecting the flesh to leaching by water either for a number of hoursat 'a temperature down to as low as 10 0., or for a short time such asminutes to a temperature between 80 C. and 100 C., and preferably withagitation, and in then separating retting, or of a chemical ormechanical separa- 10 the pretreated flesh for further treatment from,tion of the fibres from the leaf or plant flesh, the previously addedwater. there remains a considerable bulk of vegetable A further part ofthe invention in the prematter coupled with a small percentage of fibretreatment of the said flesh may also be toadd a which is normally awaste product. It is the pur- 15 ,small quantity of an aqueous solutionof a bleachpose of our present invention to provide improveing agent tothe cold or hot leaching or washing 1 ments in the treatment andutilisation of this water such as sodium hypochlorite. It is preferfleshmaterial forv the recovery of definite comable that such bleaching agentshould be added to mercial products. the leaching or washing water,whether hot or Our analyses of and experiments upon this cold before theflesh is immersed therein. fleshy material have shown that it contains aAdditionally or alternatively to the above variety of materials ofcommercial value and treatments and dependent upon the pectic inter aliawater soluble materials of a glucosidic products required, and as hereinset out, the said and also of a protein-like nature; pectic subraw orpretreated plant fiesh-may be washed at stances; and ligno-cellulose.room temperature with a dilute acid that has a Whilst extractionprocesses are known for the soluble calcium salt. removal of glucosidesand colouring matters and e The dewatered flesh remaining from the abovealso for the extraction and recovery of colloidal pretreatment processor processes is now in a very pecticsubstances without submitting theplant suitable condition for the extraction ofthe pecflesh to apreparatory process of controlled treattic products and this embracesthe production of ment, the products yielded heretofore both inalkali-metal pectates, of other metallic pectates, quality and quantityare far below those known of ammonium pectate and pectin as set out tobe present, the colour is unsatisfactory and hereafter. I their purityleaves much to be desired. Pectic products. 01' substances as herein Ithas 150 be r memb red that al Veg table described are to be understoodto include allthose products after severance from the live plantpolymeric substances recurring in or latent in the su fer r tend t er ra ry han i plant flesh that are characterised by giving rise duced y nat o e yme a t on, degradaon depolymerisation togalacturonic acid,galaction under actinic influences and. the like and 1 arabinose andrelated compounds. They these a m t 01' te d to augment factors in- 40consist essentially of polygalacturonic acids, with hibitory toextraction present in the fresh cut or witho t galactans and arabans inphysical etation. e admixture 'or chemical association, and the n O j ofe present invention is to remove simple derivatives thereof, such as thesalts of by a controlled p -t at n of t flesh the polygalacturonic acid,and the methyl esters of Said inhi tory Ct enabling much large! andpolygalacturonic acid that are known as pectins more stable yields ofproducts to be obtained, all pectinic id v g all improved appearance,01011? and A preferred manner of operating the invention ysis. e is setout below with a series of practical exam- It is a further object of theinvention to proples, but wherein it may be necessary to make videprocesses suitable for the extraction, from appropriate ll d i tion f oth figures the flesh so pretreated, of the pectic products given'toallow for (a) agegof plant,-;(b), soil in therein, said extraction bythe processes now to hi h it has grown, (0)" season of cutting, (d) bedesc b d being more complete and the type of decortication, (e) periodof delay between products purer and of better phys properties, cuttingand process treatment. Examples 1 to 6 than have heretofore beenpossible. 5 refer to the pretreatment processes, Examples 7 to 10 to theextraction processes we have found to be suitable-for the pre-treatedflesh. e Erample L -The flesh is leached with 15 to 30 should beallowed.

Z 'fore the addition of 1 that afsuitableamount is 2- /2 litres ofcommercial sodium hypochlorite solutionof strength to times its weightof water, preferably "soft water, 1 for 24 hours at 10 C. to 0.,preferably with agitation, and is then separated from the liquor 3 bydraining, and washed. if desired with more; water. l

Example 2.The flesh is leached with is 'to so 1 times its weight ofwater, preferably soft water,

at 80 Cyto 1100 C., preferably v1 i with agitation, and is thenseparated jfrom'the 1 1' liquor by draining, I

j,water.1 It is understood that lower temperatures 1 such as C. to 75 C.maybe used when corfor% to /2 hourv and washed if desired bymorerespondingly longer periods of timeforleaching Examplei-To the leachingwater as in Examples 1 or 2 is added a quantity of a bleaching 3 agentsuch as sodium hypochlorite, preferably bethe flesh. We have found 1every to '70 gallons of leaching water, butit of analkali-metal or"ammonium salt having an. alkaline reaction, of which the anion gives aninsoluble salt with calcium ions. Thus .sodium carbonate or trisodiumphosphate or sodium will be understood that the amount to be used will1.

depend on the colour and condition-of the flesh being processed and mayhave to be determined on each batch by trial. 7

Example 4.--'To the washing'water as in Examples 1 or 2 is added ableaching agent such as sodium hypochlorite, as described'in Example 3.A further wash with water may be given if desired;

Example 5. Io. the leaching water, as in Example 1 is'added 2% to5 byvolume of com-, mercial' concentrated hydrochloric acid and the leachingis allowed to proceed for to 5 hours;

' This treatment results in a change in: the pectic substances withinthe flesh, but does not pro-,

duce their extraction; and on washing out the-1 excess acid andproceeding to any of the pectic extractions as set out in Examples 7 to10'we every case, in at lower temfind that these are made easier in thatthey proceed {to completion peratures 7 Furthermore in the extraction ofpectate, alkali'es not containing calcium-precipitating anions can beused, for instance sodium hydroxide; and in the extraction ofpectinj-mor dilute reagents can be used, doubtless because the acidsoaking removes a good deal ofthe calcium from the flesh by breakingdown calcium pectate linkages and dissolving any able amounts andconditions are:

Flesh 0.5 hydrochloric acid 15 used cold for three hours. The resultingflesh free calcium carbonate. S uitand .in some cases in less time.

Parts by weight i after being washed with cold water to remove excesshydrochloric acid gives immediate extraction of some pectate in thecoldand a good yield at 80 C. when processed according "to Example 7. vThe dilute hydrochloric acid may be removed and used over again. I 7

Example 6.To the washing water as in Examples 1 or 2 is addedhydrochloric acid as described in Example 5 and the dilute acid ismaintained in contact with the flesh for to 5 hours at room temperature,after which it is,

washed out with-more water. This acid wash may also be applied to theflesh first treated either according 'to EXa-mple 3 or 4, if anintermediate-wash with water-is given to remove'excess sodium'hypochlorite before the addition of acid.

Example" 7-The flesh pre-treate'd according V to any of Examples 1 to 6is-m-ixed with-a=solution taining at the factory, for

meta-silicate are suitable extracting agents. The effect of theextracting agent is two-fold; it hydrolyses any methoxy groups in theprotopectin of the plant material, and it decomposes linkages in theprotopectin any calcium pectate with the formation of an insolublecalcium salt; the alkali-metal salt of pectic acid is thus produced andthis dissolves colloidally in the aqueous extracting solution.Convenient amounts of the materials are:

' Parts by weight Flesh 1 Water 30 Sodium carbonate (anhydrous):w 02 theextraction being carried on for 15 to 3.0

minutes at60'C. to C. with stirring. It will be understood that theseamounts, times and temperatures are given by way of example only and maybe widelyvaried according to the particular sample of raw materiahtheconditions obof time, fuel and sodium carbonate available, and thenature of the product desired. Indeed, the extraction using the aboveformula may be made in the cold, at say'ZG" C.'if the time allowable isof the order of 24 hours, and if the highest percentagev yield is not aprime consideration;

It should be understood that the amount, of fflesh specified in thisexample and all other examples herein refers to the original weight ofair-dry flesh taken before pre-treatment,

' When trisodium phosphate is used for thee);- traction this-mayparticularly wellbe made at comparatively 'low temperatures, aconvenient formula being. A

7 Parts by weight Flesh "1 'Water "a. 30

'Irisodium phosphate 0:25

used at a temperature of 30C. with stirring, for /2 to 2 hours.

The alkali-metal "pectate either ofthese extractions orequivalent'processes using other suitable alkali-:metal salt solutions,is filtered off, and from it is precipitatedeither:

(a) Alkali-metal pectate,-which may be produced either by the additionofalcoh01, acetone or like water-miscible organic solvent, or by theaddition of a concentrated solution of sodium chloride (say 30/35 byweight), sodium sulphate or other electrolyte that does not react withthe alkali-metal pectate. I The gelatinous precipitate of alkali-metalpectate ,is collected, dried and ground, and is then a marketableproduct taking the form of a white or nearly white powder, readilydispersible in water to form viscous tions or gels; the whiteness of theproduct may be improved by adding a small proportionof sodiumhypochlorite solution before or during the precipitation.

(b) 'Pectic acid which may be produced by the addition ofany acid(hydrochloric acid being suitable) having a dissociationconstant'great'er thanvabout 10- to thealkali-metal pectate'sol: aflocculentprecipitate is produced which is collected by settlement orfiltration, and which is dried and powdered as under (11) It is a nearlywhite powder soluble in I alkaline solutions, sparingly soluble inwater. When-the'extr'action has example, the amount I sol "resultingfrom solu-,

been made with sodium meta-silicate the pectic acid floc may containalso silicic acid.

Metallic pectates, produced by the addition of a dilute solution of awater-soluble metallic salt to the alkali-metal pectate sol, whose pI-Ihas previously been brought to a value of 7 or less by the cautiousaddition of an acid such as hydrochloric, nitric or acetic acids, andfrom which adjusted solution excess carbon dioxide (in the case of anextraction made with sodium carbonate) has preferably been boiled off orblown off with a current of air, and which has preferably been dilutedif necessary so that it contains not more than A;% of ectate; forexample, zinc chloride, nickel chloride, silver nitrate or calciumchloride solutions may be added to give zinc pectate, nickel pectate.silver pectate and calcium pectate respectively as flocculentprecipitates which may be removed, dried and powdered as before. Thesepectates are insoluble in water.

When it is desired to prepare ammonium pectate, this may be produced asa sol by the dissolution of pectic acid in ammonia or directly from theflesh by extraction with a solution of ammonium phosphate, under thesame conditions as those stated above for trisodium phosphate,

except that the temperature should be about 20 C. higher.

Example 8.If the extraction of the flesh pretreated according to any ofExamples 1 to 6 is carried out by means of a solution of an alkalimetalsalt having an anion that forms watersoluble complexes with calcium,then if the solution has a pH below 7, pectin is extracted, whereas ifthe solution is substantially alkaline, alkalimetal pectate is theproduct. Such alkali-metal salts are the hexametaphosphates,pyrophosphates and the like, and a suitable formula for making thepectin extraction is:

Parts by weight Flesh 1 Acid sodium h'exametaphosphate 0.1 Water 30 usedat boiling point for to 30 minutes. The same formula, but with theliquor adjusted to pH 9-10 with sodium hydroxide or other alkali, may beused to give an extract of sodium pectate. From the sols produced,alkali-metal pectate is obtained in the dry condition by means ofprocesses similar to those already set out or referred to, in Example 7,while pectin is obtained by salting out or by other known means.

Example 9.When the flesh has been pretreated according to Examples 5 or6, the extraction of pectic substances may be achieved by the use ofalkaline solutions not containing anions forming insoluble calcum-saltsor soluble calcium complexes. Thus, ammonia or the alkali-metalhydroxides may be used. The conditions as to amounts, times andtemperatures may be widely varied, but are in general similar to thosegiven in Examples 7 and 8. In particular it may be mentioned thatpartial extraction by ammonia solution can be achieved under thefollowing conditions:

' Parts by weight Flesh 1 Water- 30 Ammonia (S. Cr. 0.880) 0.5

used at room temperature for 4 hour.

Example Ill-The flesh pre-treated according to any of Examples 1 to 6 isin a very favourable condition for the'extraction of pectin. Inparticular, a suitable formula is:

Parts by Weight Flesh Ammonium oxalate 0.3 Water 40 ous electrolytehaving a pH of about 5 or less,

but that the conditions stated above have been found especially suitablefor the particular pretreated flesh herein described.

We claim:

1. In a process for the treatment of plant flesh and for the recovery ofpectic substances therefrom, comprising stripping the flesh from thefibrous backbone of the plant, pretreating the stripped flesh byleaching with water for a length of time and at a temperatureinsufficient to effect extraction of pectic substances from the flesh,washing the flesh with water, then separating the pretreated flesh andextracting the pectic substances therefrom; the improvement whichcomprises employing a cold solution not exceeding about 2% to 5% byvolume of commercialhydrochloric acid during the pretreating stage andprior to extraction of the pectic substances for tionof the pecticsubstances.

2. A process as set forth in claim 1 wherein hypochlorite is added tothe leaching water.

3. A process asset forth in claim 1 wherein hypochlorite is added to thewashing water;

4. A process as set forth in claim 1 wherein cold hydrochloric acid isadded to the leaching water. 5. A process as set forth in claim 1wherein cold hydrochloric acid is added to the washing water.

6. A process as set forth in claim 1 wherein the pectic substances areextracted from the pretreated flesh by treating said flesh with anaqueous alkaline solution containing a member of a. group consisting ofalkali metal and ammonium salts having an alkaline reaction, ofwhich-the anion gives an insoluble salt with calcium ions.

- THOMAS PERCY HOAR.

ELSIE LILIAN JAMES.

REFERENCES CITED UNITED STATES PATENTS Name Date Wallerstein -1 July 23,1935 OTHER REFERENCES American Jour. of Botany, November 1926, pages536-543.

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